U.S. patent number 5,791,686 [Application Number 08/611,995] was granted by the patent office on 1998-08-11 for energy absorbing intermediate steering shaft.
This patent grant is currently assigned to NSK Ltd.. Invention is credited to Seiichi Moriyama.
United States Patent |
5,791,686 |
Moriyama |
August 11, 1998 |
Energy absorbing intermediate steering shaft
Abstract
An energy absorbing type intermediate shaft structure to be
incorporated into a steering device of an automobile for
transmitting a steering force of a steering wheel to a steering
gear, has a shaft inserted in a tube. The shaft has a small
cross-sectional area portion and a pressing portion. A cover tube
is present around the small cross-sectional area portion. The
location at which the pressing portion is formed is regulated so
that with the pressing portion bearing against the cover tube, one
end edge of the cover tube may lie around the small cross-sectional
area portion. A distance .alpha. between the pressing portion and
the cover tube, a distance .beta. between the cover tube and the
tube, and a distance .gamma. between the shaft and a member
associated with a yoke in the steering device are set to satisfy
the condition .alpha.+.beta.<.gamma..
Inventors: |
Moriyama; Seiichi (Takasaki,
JP) |
Assignee: |
NSK Ltd. (Tokyo,
JP)
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Family
ID: |
13299514 |
Appl.
No.: |
08/611,995 |
Filed: |
March 5, 1996 |
Foreign Application Priority Data
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Mar 24, 1995 [JP] |
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7-065872 |
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Current U.S.
Class: |
280/777; 74/492;
464/162 |
Current CPC
Class: |
B62D
1/192 (20130101) |
Current International
Class: |
B62D
1/19 (20060101); B62D 001/19 () |
Field of
Search: |
;280/777 ;74/492
;464/162,179 ;188/371,376 |
References Cited
[Referenced By]
U.S. Patent Documents
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5580314 |
December 1996 |
Moriyama et al. |
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Foreign Patent Documents
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0 683 084 |
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Nov 1995 |
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EP |
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3-79472 |
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Apr 1991 |
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JP |
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6-72779 |
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Oct 1994 |
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JP |
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7-309241 |
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Nov 1995 |
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JP |
|
Primary Examiner: English; Peter C.
Attorney, Agent or Firm: Shapiro and Shapiro
Claims
What is claimed is:
1. For a steering apparatus of an automobile that transmits a
steering force of a steering wheel to a steering gear, an energy
absorbing intermediate shaft structure for absorbing a strong axial
force applied thereto, comprising:
a tube portion having a first end and a second end;
a shaft inserted into said second end of said tube portion and
being non-rotatable relative to said tube portion, said shaft
having an end face opposing a member disposed on said tube portion
toward said first end thereof, said shaft also having a small
cross-sectional area portion formed in an intermediate portion of
said shaft that is disposed away from said tube portion;
a displacement limiting portion provided between said shaft and
said tube portion which enables relative axial displacement of said
shaft and said tube portion only when said strong axial force is
applied;
a reinforcing member surrounding said shaft so as to cover said
small cross-sectional area portion; and
a pressing portion disposed on said shaft and arranged to bear
against a first end face of said reinforcing member only when said
strong force is applied, thereby pressing said reinforcing
member,
wherein a second end face of said reinforcing member and an
opposing end face of said tube portion are inclined relative to
each other,
said pressing portion is formed at a position such that, when said
pressing portion bears against said first end face of said
reinforcing member, said second end face of said reinforcing member
is disposed around said small cross-sectional area portion, and
a sum, prior to application of said strong axial force, of a
distance from said pressing portion to said first end face of said
reinforcing member and a closest distance from said second end face
of said reinforcing member to said end face of said tube portion is
made smaller than a distance from said end face of said shaft to
said member disposed on said tube portion.
2. For a steering apparatus of an automobile that transmits a
steering force of a steering wheel to a steering gear, an energy
absorbing intermediate shaft structure for absorbing a strong axial
force applied thereto, comprising:
a tube portion having a first end and a second end;
a shaft inserted into said second end of said tube portion and
being non-rotatable relative to said tube portion, said shaft
having an end face opposing a member disposed on said tube portion
toward said first end thereof, said shaft also having a small
cross-sectional area portion formed in an intermediate portion of
said shaft that is disposed away from said tube portion;
a displacement limiting portion provided between said shaft and
said tube portion which enables relative axial displacement of said
shaft and said tube portion only when said strong axial force is
applied;
a reinforcing member surrounding said shaft so as to cover said
small cross-sectional area portion; and
a pressing portion disposed on said shaft and arranged to bear
against a first end face of said reinforcing member only when said
strong force is applied, thereby pressing said reinforcing
member,
wherein one of a second end face of said reinforcing member and an
opposing end face of said tube portion has diametrically opposite
portions that are axially offset from each other,
said pressing portion is formed at a position such that, when said
pressing portion bears against said first end face of said
reinforcing member, said second end face of said reinforcing member
is disposed around said small cross-sectional area portion, and
a sum, prior to application of said strong axial force, of a
distance from said pressing portion to said first end face of said
reinforcing member and a closest distance from said second end face
of said reinforcing member to said end face of said tube portion is
made smaller than a distance from said end face of said shaft to
said member disposed on said tube portion.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to an energy absorbing type intermediate
shaft structure incorporated in the steering apparatus of an
automobile and utilized to transmit a steering force of a steering
wheel to a steering gear.
2. Related Background Art
In a steering apparatus for an automobile, a mechanism as shown in
FIG. 8 of the accompanying drawings is used to transmit a steering
force of a steering wheel to a steering gear. In FIG. 8, the
reference numeral 1 designates a steering shaft having a steering
wheel 2 fixed to its upper end portion, and the reference numeral 3
denotes a steering column fixed to the underside of an instrument
panel 6 by upper and lower brackets 4 and 5. The steering shaft 1
is rotatably inserted in the steering column 3.
The upper end portion of an intermediate shaft 8 is connected to
the lower end portion of the steering shaft 1 which protrudes from
the lower end opening of the steering column 3, through a first
universal joint 7. Further, the lower end portion of this
intermediate shaft 8 is connected to the input shaft 10 of a
steering gear (not shown) through a second universal joint 9.
With such a construction, the movement of the steering wheel 2 is
transmitted to the steering gear through the steering shaft 1, the
first universal joint 7, the intermediate shaft 8, the second
universal joint 9 and the input shaft 10, whereby a steering angle
is given to wheels.
Now, in the thus constructed steering mechanism, in order to
protect a driver during a collision, it has been generally
practised to make the steering column 3, the steering shaft 1 and
the intermediate shaft 8 into an energy absorbing type in which
with a shock, their full length shrinks while they absorb the
energy of the shock. As an energy absorbing type intermediate
shaft, there is known one described, for example, in Japanese
Patent Application Laid-Open No. 3-79472.
A first example of the energy absorbing type intermediate shaft 8
according to the prior art described in the above-mentioned
publication, as shown in FIG. 9 of the accompanying drawings, is
comprised of a combination of four members, i.e., a shaft 11, a
connecting tube 15, a connecting shaft 18 and a tube 20. These
members 11, 15, 18 and 20 are combined together with male spline
grooves 13, 13 which are formed in one end portion (the right end
portion as viewed in FIG. 9) of the shaft 11 and the opposite end
portions of the connecting shaft 18 being engaged with female
spline grooves 16, 16 which are formed in the opposite end portions
of the connecting tube 15 and one end portion (the left end portion
as viewed in FIG. 9) of the tube 20. In this state, the depth D
from one end opening (the left end opening as viewed in FIG. 9) of
the tube 20 to the end surface of a yoke 21 fixed to the other end
portion (the right end portion as viewed in FIG. 9) of the tube 20
is equal to the length L of the connecting shaft 18 (D=L).
Further, synthetic resin 22a-22d is poured into concave grooves
14a-14d formed in the shaft 11 and the connecting shaft 18 through
through-holes 17a-17d formed in the connecting tube 15 and the tube
20 and is solidified to thereby couple the members 11, 15, 18 and
20 together. As a result, these members 11, 15, 18 and 20 are
coupled together against displacement in the direction of rotation
and displacement in the axial direction (the left to right
direction as viewed in FIG. 9) thereof. In the state in which the
members 11, 15, 18 and 20 are thus combined together, a gap 23 is
formed between one end surface (the right end surface as viewed in
FIG. 9) of the shaft 11 and one end surface (the left end surface
as viewed in FIG. 9) of the connecting shaft 18, and a gap 24 is
formed between the other end surface (the right end surface as
viewed in FIG. 9) of the connecting shaft 18 and the end surface of
the yoke 21. Also, the connecting shaft 18 is extended between the
connecting tube 15 and the tube 20 and enables the transmission of
a rotational force between these two tubes 15 and 20 and in
addition, prevents the abutting portions of these two tubes 15 and
20 from being bent.
When an automobile having the intermediate shaft 8 constructed as
described above incorporated in the steering apparatus thereof
collides and the front of this automobile is crushed, the second
universal joint 9 comprising the yoke 12 is pushed rearwardly
(rightwardly as viewed in FIG. 9) and the synthetic resin 22a, 22b
connecting the shaft 11 and the connecting tube 15 together is
first torn by a compression force applied to the intermediate shaft
8, and the shaft 11 is displaced rearwardly by an amount
corresponding to the gap 23 and thus, one end surface of the shaft
11 and one end surface of the connecting shaft 18 which are opposed
to each other come into collision with each other.
When the shaft 11 is further pushed rearwardly from this state, the
synthetic resin 22c, 22d provided between the connecting shaft 18
and the connecting tube 15 and between the connecting shaft 18 and
the tube 20 is torn and the connecting shaft 18 is displaced
rearwardly by an amount corresponding to the gap 24, and the other
end surface (the right end surface as viewed in FIG. 9) of the
connecting shaft 18 and the end surface of the yoke 21 come into
collision with each other. In this state, one end edge of the tube
20 and one end surface of the connecting shaft 18 lie on the same
plane. Accordingly, the coupling support force of the tube 20 and
the connecting tube 15 by the connecting shaft 18 (the force
preventing the tubes 20 and 15 from bending) is lost.
As a result, the shaft 11 and the connecting shaft 18 separate from
each other in such a manner as to bend, and the shaft 11 no longer
pushes the connecting shaft 18 and the tube 20 rearwardly.
Accordingly, even if, during the collision, the second universal
joint 9 is pushed rearwardly, it will no longer happen that the
first universal joint 7 is pushed rearwardly, whereby the steering
wheel 2 will be prevented from jutting out toward the driver side
to thereby prevent impartation of any danger to the driver.
Now, in the case of such an energy absorbing type intermediate
shaft heretofore known, with the four members 11, 15, 18 and 20
which are constructed independently of one another being combined
together in predetermined positional relationship, they are coupled
together against displacement by the synthetic resin 22a-22d.
Therefore, the assembling work has been cumbersome and the cost of
manufacture has unavoidably increased. Also, because the shaft 11
and the connecting shaft 18 are divided into two, three or more
backlash preventing means become necessary between the shafts 11,
18 and the tubes 15, 20. Therefore, the fit length between the
shafts 11, 18 and the tubes 15, 20 becomes necessary to a certain
degree, and this gives rise to problems such as the increased full
length of the intermediate shaft 8, the cumbersomeness of the
incorporating work and the difficulty in securing the crush
allowance of the intermediate shaft 8.
In order to solve such problems, Japanese Utility Model Application
Laid-Open No. 6-72779 describes an energy absorbing type
intermediate shaft in which the number of parts is reduced to
thereby simplify the assembling work and achieve a reduction in
cost of manufacture. The second example of the energy absorbing
type intermediate shaft according to the prior art described in
this publication, as shown in FIG. 10 of the accompanying drawings,
is provided with a tube 25, a shaft 26 and a displacement limiting
portion 33. The shaft 26 is made not rotatable relative to the tube
25 by male spline grooves 29 formed in the outer peripheral surface
of that portion of the shaft 26 which is near one end (the right
upper end as viewed in FIG. 10) thereof being engaged with female
spline grooves 28 formed in the inner peripheral surface of that
portion of the tube 25 which is near one end (the left lower end as
viewed in FIG. 10) thereof. The displacement limiting portion 33
enables the relative axial displacement of the shaft 26 and the
tube 25 only when an axial strong force is applied to the
intermediate shaft 8a, and is constructed as follows.
A concave groove 30 formed in the outer peripheral surface of one
end portion (the right upper end portion as viewed in FIG. 10) of
the shaft 26 is filled with synthetic resin 32 through
through-holes 31, 31 formed in the outer peripheral surface of the
intermediate portion load the tube 25. In the case of the
illustrated example, the synthetic resin 32, after filling the
concave groove 30, is torn between the through-holes 31, 31 and the
concave groove 30. The limitation of the displacement of the two
members 25 and 26 is provided by a frictional force acting between
these members 25 and 26. This is for mitigating and stabilizing the
load required for the shaft 26 and the tube 25 to begin to displace
in case of a collision accident.
Further, a stopper portion is provided on the other end portion
(the right upper end portion as viewed in FIG. 10) of the tube 25.
This stopper portion serves to limit the amount of insertion of the
shaft 26 into the tube 25 and in the case of the illustrated
example, a pin 34 inserted in circular holes 38 and 37 formed in a
yoke 36 and a shock absorbing tube 35, respectively, constituting a
first universal joint 7 provides this stopper portion. Also, the
intermediate portion of the shaft 26 is provided with a small
cross-sectional area portion 39 concentric with the shaft 26 and
sufficiently small in diameter as compared with the other portions
of the shaft 26. The circumference of the portion on which this
small cross-sectional area portion 39 is formed is covered with a
cover tube 27. This cover tube 27 is supported around the shaft 26
for axial displacement only. That is, female spline grooves 40 are
formed in the inner peripheral surface of the cover tube 27 and are
spline-engaged with the male spline grooves 29 formed in the outer
periphery of the shaft 26. The portion between the cover tube 27
and the small cross-sectional area portion 39 is filled with
synthetic resin 42 through through-holes 41, 41. Further, the depth
D' from one end edge of the tube 25 to the side of the pin 34 is
made equal to the length L' from one end surface of the shaft 26 to
the center of the small cross-sectional area portion 39.
Accordingly, in a state in which one end surface of the shaft 26
strikes against the side of the pin 34, one end edge of the tube 25
lies around the intermediate portion of the small cross-sectional
area portion 39.
The action when the second example of the energy absorbing type
intermediate shaft according to the prior art constructed as
described above transmits the movement of the steering wheel 2
(FIG. 8) to the steering gear is substantially similar to that in
the case of the aforedescribed first example of the intermediate
shaft according to the prior art. Also, in the case of the present
structure, the cover tube 27 is present around the portion on which
the small cross-sectional area portion 39 is formed and therefore,
it does not happen that the shaft 26 bends at this small
cross-sectional area portion 39. During a collision, the front of
an automobile is crushed and the second universal joint 9 is pushed
rearwardly (rightwardly as viewed in FIG. 10), whereby an axial
strong compressive force is applied to the intermediate shaft 8a,
the shaft 26 is pushed into the tube 25 against a frictional force
present in the displacement limiting portion 33. Then, one end edge
of the tube 25 and one end edge (the right upper end edge as viewed
in FIG. 10) of the cover tube 27 abut with each other. Further, the
synthetic resin 42 present around the small cross-sectional area
portion 39 is torn and the shaft 26 is pushed farther into the tube
25 until one end surface of this shaft 26 strikes against the side
of the pin 34. In this process, one end edge of the tube 25 pushes
and moves the cover tube 27 from around the small cross-sectional
area portion 39 and thus, one end edge of the tube 25 comes to lie
around the small cross-sectional area portion 39.
When in this state, the above-mentioned compressive force is
further applied, the shaft 26 bends at the small cross-sectional
area portion 39, as shown in FIG. 11 of the accompanying drawings,
and by the second universal joint 9, an impact force applied from
the fore end side (the left end side as viewed in FIG. 10) of the
intermediate shaft 8a is prevented from being transmitted to the
first universal joint 7 provided on the rear end side (the right
end side as viewed in FIG. 10) of the intermediate shaft 8a. The
synthetic resin 42 filling the portion around the small
cross-sectional area portion 39 is smashed and falls when the shaft
26 bends.
The above-mentioned Japanese Utility Model Application Laid-Open
No. 6-72779 also describes structure in which, as shown in FIGS. 12
and 13 of the accompanying drawings, one end edge (the right upper
end edge as viewed in FIGS. 12 and 13) of a cover tube 27a is
inclined. In the case of such structure, in a state in which one
end surface of a shaft 26 is pushed in until it strikes against a
pin 34, the cover tube 27a retracts from around a small
cross-sectional area portion 39 (FIG. 12) and further, by a
compressive force being applied to the shaft 26, this shaft 26 is
bent by a relatively light force (FIG. 13). That is, in a state in
which the cover tube 27a retracts from around the small
cross-sectional area portion 39 and as shown in FIG. 12, the small
cross-sectional area portion 39 lies inside the abutting portion
between the cover tube 27a and a tube 25, a receiving portion 46
formed on the shaft 26 bears against the other end edge of the
cover tube 27a. At this time, one end surface of the shaft 26 bears
against a pin 34, as shown in FIG. 11. In this state, the movement
of the cover tube 27a is blocked. Therefore, when a compressive
force is further applied to the shaft 26, the cover tube 27a is
pushed between the receiving portion 46 and the tube 25 pushed by
the pin 34 (see FIGS. 10 and 11). As a result, the shaft 26 bends
at the small cross-sectional area portion 39 with one end surface
thereof bearing against the pin 34. In the case of the second and
third examples of the energy absorbing type intermediate shaft
according to the prior art as described above, as compared with the
structure of the aforedescribed first example of the prior art,
sufficient energy absorbing capability is secured, and yet the
number of parts can be reduced to thereby achieve simplification of
the assembling work and thus, a reduction in cost of
manufacture.
Further, the present applicant previously invented an energy
absorbing type intermediate shaft keeping the effects of the
structure of the aforedescribed second example of the prior art and
capable of further reducing the cost of manufacture (Japanese
Patent Application No. 6-106672). The energy absorbing type
intermediate shaft 8b of this previous invention regulates the
dimension of a small cross-sectional area portion 39a as shown in
FIG. 14 of the accompanying drawings to thereby eliminate the
necessity of strictly regulating the working accuracy of the male
and female spline grooves 29 and 40 and achieve a reduction in the
cost of manufacture.
That is, the outer diameter r.sub.39a of the small cross-sectional
area portion 39a is 1/4 to 1/2 of the outer diameter R.sub.26 of
the shaft 26 (r.sub.39a =(1/4 to 1/2) R.sub.26). The outer diameter
r.sub.39a of the small cross-sectional area portion 39a is the
outer diameter of the intermediate portion of this small
cross-sectional area portion 39a forming a pillar-like shape. Also,
the length 1.sub.39a of this small cross-sectional area portion 39a
is two or more times as great as the outer diameter r.sub.39a of
this small cross-sectional area portion 39a (1.sub.39a
.gtoreq.2r.sub.39a). The length 1.sub.39a of the small
cross-sectional area portion 39a is the length of only the
pillar-like portion of this small cross-sectional area 39a
excluding arcuate portions 43, 43 present on the opposite end
portions thereof. In the other points, the construction of the
previous invention is similar to the structure of the
aforedescribed second example of the prior art. In the case of the
structure of the previous invention, concave grooves 44 are formed
in portions of the shaft 26 adjacent the small cross-sectional area
39a, and these concave grooves 44 are filled with synthetic resin
42 through through-holes 41, 41 formed in a cover tube 27. The
portion around the small cross-sectional area portion 39a is not
filled with synthetic resin.
When the energy absorbing type intermediate shaft of the previous
invention (constructed as described above) is incorporated into the
steering apparatus of an automobile whereby the movement of the
steering wheel 2 (FIG. 8) can be transmitted to the steering gear
the following action takes place during a collision. The energy
absorbing type intermediate shaft 8b plastically deforms the small
cross-sectional area portion 39a when an axial strong compressive
force is applied thereto, whereby it is bent and absorbs energy
based on the collision to thereby alleviate the shock applied to a
driver's body. Thus, the operation is similar to that of the case
of the structure of the aforedescribed second example of the prior
art.
However, in the case of the energy absorbing type intermediate
shaft 8b of the previous invention, the dimensions of the small
cross-sectional area portion 39a are regulated as described above
and therefore, even if backlash is present in the spline-engaged
portion between the cover tube 27 and the shaft 26 and the shaft 26
is more or less displaced in the direction of rotation relative to
the cover tube 27, the small cross-sectional area portion 39a will
be sufficiently deformed in the direction of torsion thereof to
thereby prevent any unnatural force from being applied to this
small cross-sectional area portion 39a. That is, since the outer
diameter r.sub.39a and length 1.sub.39a of the small
cross-sectional area portion 39a are regulated as described above,
the torsion allowing angle of this small cross-sectional area
portion 39a becomes great. As a result, even when this small
cross-sectional area portion 39a is resiliently deformed on the
basis of a rotational torque, the stress created in this small
cross-sectional area portion 39a becomes small and even by a
rotational torque applied repetitively thereto, it becomes
difficult for any damage based on metal fatigue to be created in
the small cross-sectional area portion 39a. Accordingly, it becomes
unnecessary to strictly regulate the dimensional accuracy of the
structural portion for blocking the rotation of the cover tube 27
and the shaft 26, i.e., the dimensional accuracy of the male spline
grooves 29 and the female spline grooves 40. As a result, an
increase in cost resulting from highly accurate working can be
prevented and the cost of manufacture of the energy absorbing type
intermediate shaft can be further reduced.
Now, the aforedescribed second and third examples of the
intermediate shaft according to the prior art and the intermediate
shaft according to the previous invention have the effect that they
are easy to manufacture and a reduction in the cost of manufacture
can be achieved. However, in the case of the structure of the
aforedescribed previous invention and the structure of the second
example of the prior art, one end surface of the shaft 26 bends in
a state in which it strikes against the pin 34. Accordingly, the
force required to bend the small cross-sectional area portion 39
(in the case of the structure of the second and third examples of
the prior art shown in FIGS. 10 to 13) or 39a (in the case of the
structure of the previous invention shown in FIG. 14) of the shaft
26 cannot always be made sufficiently small.
That is, in the aforedescribed prior-art structure (including the
structure of the previous invention), in a state in which as shown
in FIG. 13, the cover tube 27a is pushed by the receiving portion
46 and a portion of one end edge (the rear end edge or the right
end edge as viewed in FIGS. 10 to 14) of the cover tube 27 (27a)
bears against one end edge (the fore end edge or the left end edge
as viewed in FIGS. 10 to 14) of the tube 25, one end surface (the
rear end surface or the right end surface as viewed in FIGS. 10, 11
and 14) of the shaft 26 has already borne against the pin 34 as
shown in FIG. 11. When from this state, the shaft 26 is further
pushed rearwardly (rightwardly upwardly as viewed in FIG. 10), the
center axes of the tubes 27 (27a) and 25 are bent on the basis of
the engagement between the rear end edge of the cover tube 27 (27a)
and the fore end edge of the tube 25, and the small cross-sectional
area portion 39, 39a of the shaft 26 inserted in these tubes 27
(27a) and 25 is bent. At this time, actually, the second half (the
right half as viewed in FIGS. 10, 11 and 14) of the shaft 26 tends
to be pushed into the tube 25. However, since the rear end surface
of the shaft 26 strikes against the pin 34, the retraction of the
shaft 26 (an increase in the amount of entry into the tube 25)
resulting from the bending of the small cross-sectional area
portion 39, 39a does not take place smoothly and the force required
for the bending of the small cross-sectional area portion 39, 39a
becomes great. Further, at this time, a strong pressure force is
applied from one end surface of the shaft 26 to the pin 34.
Accordingly, it is necessary to secure the rigidity of this pin 34
sufficiently. As a result, the cost of manufacture of the pin 34
increases correspondingly. The energy absorbing type intermediate
shaft of the present invention has been thought out in view of the
circumstances as described above.
SUMMARY OF THE INVENTION
An energy absorbing type intermediate shaft of the present
invention is provided with a tube, a shaft inserted in the tube
from one end opening side of the tube against rotation relative to
the tube, a displacement limiting portion provided between the
shaft and the tube for enabling the axial displacement of the shaft
and the tube only when a strong axial force is applied thereto, a
small cross-sectional area portion formed in that portion of the
intermediate portion of the shaft which is off the tube, a
reinforcing member provided around the shaft for axial displacement
only covering the circumference of the small cross-sectional area
portion, and a pressing portion secured to the outer peripheral
surface of the shaft and adapted to bear against the other end edge
of the reinforcing member only when said strong force is applied,
thereby pressing the reinforcing member. At least one of one end
edge of the reinforcing member and one end edge of the tube which
are opposed to each other is inclined in a direction in which one
half side thereof is more spaced apart from the other end edge than
the other half side. The pressing portion has its formed position
regulated so that with the other end edge of the reinforcing member
bearing against the pressing portion, one end edge of the
reinforcing member may lie around the small cross-sectional area
portion. The sum of the distance from the pressing portion to the
other end edge of the reinforcing member before said strong force
is applied and the gap distance between one end edge of the tube
and one end edge of the reinforcing member which are opposed to
each other is made smaller than the distance from one end surface
of the shaft to a member provided on the other end portion of the
tube and to which said one end surface is opposed.
In the case of the energy absorbing type intermediate shaft of the
present invention constructed as described above, during the normal
time (before a strong force is applied), the reinforcing member is
present around the small cross-sectional area portion of the
intermediate portion of the shaft. Therefore, it never happens that
the shaft bends at this small cross-sectional area portion. When
during a collision, an axial strong compressive force is applied,
the shaft is first pushed into the tube against the limiting force
of the displacement limiting portion. In this process, one end edge
of the reinforcing member and one end edge of the tube bear against
each other by their respective halves, and further one end edge of
the tube pushes and moves the reinforcing member from around the
small cross-sectional area portion. The pressing portion then bears
against the other end edge of the reinforcing member, and the
reinforcing member is pressed by this pressing portion. Thus, one
end edge of the tube comes to lie around the small cross-sectional
area portion. In the case of the present invention, however, it
never happens that with one end edge of the tube lying around the
small cross-sectional area portion, one end surface of the shaft
strikes against the member provided on the other end portion of the
tube and to which said one end surface is opposed.
When said compressive force is applied with one end edge of the
tube lying around the small cross-sectional area portion, the shaft
bends at the small cross-sectional area portion to thereby prevent
an impact force applied from the fore end side of the energy
absorbing type intermediate shaft from being transmitted to the
rear end side of this intermediate shaft. When the shaft bends, one
end surface of the shaft is not bearing against said member, and
even if the amount of entry of the shaft into the tube resulting
from the bending of the small cross-sectional area portion
increases, said one end surface will not bear against said member.
Accordingly, in the case of the energy absorbing type intermediate
shaft of the present invention, the shaft is bent by a light force
when the shock during a collision is applied thereto.
Further, a pressure force applied to the member provided on the
other end portion of the tube and to which one end surface of the
shaft is opposed, such as a pin for supporting the base end portion
of a universal joint is practically decreased as compared with the
case of the previous invention. Therefore, the rigidity of said
member need not be made so great as that of the member provided on
the other end portion of the tube in the structure of the second
and third examples of the prior art or the structure of the
previous invention. That is, by the reason that the distance
between the point of application of the compressive force acting on
this member and the fulcrum becomes shorter and the moment becomes
smaller, the structure of the present invention becomes smaller in
the stress. Accordingly, when the member provided on the other end
portion of the tube is to be manufactured, the rigidity thereof can
be made smaller. Thus, the cost of manufacture of this member can
be reduced to thereby reduce the cost of manufacture of the entire
energy absorbing type intermediate shaft.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a cross-sectional view corresponding to the portion A of
FIG. 8 but showing an embodiment of the present invention.
FIG. 2 is a cross-sectional view of principal portions of the FIG.
1 embodiment showing the state of the first stage in a
collision.
FIG. 3 is a cross-sectional view similar to FIG. 2 but showing the
second stage in the collision.
FIG. 4 is a cross-sectional view showing one end surface portion of
a shaft at the second stage in the collision.
FIG. 5 is a cross-sectional view similar to FIG. 2 but showing the
third stage in the collision.
FIG. 6 is a cross-sectional view similar to FIG. 4 but showing one
end surface portion of the shaft at the third stage in the
collision.
FIG. 7 is a cross-sectional view similar to FIG. 2 but showing the
last stage in the collision.
FIG. 8 is a side view showing an example of a prior art steering
apparatus incorporating therein an energy absorbing type
intermediate shaft.
FIG. 9 is a half cross-sectional view showing the structure of a
first example of the prior art.
FIG. 10 is a cross-sectional view showing the structure of a second
example of the prior art.
FIG. 11 is a cross-sectional view similar to FIG. 10 but showing
the bent state of the shaft.
FIG. 12 is a cross-sectional view showing the essential portions of
a third example of the structure of the prior art in a stage in a
collision similar to the stage in FIG. 3.
FIG. 13 is a cross-sectional view similar to FIG. 12 but showing
the FIG. 12 structure at the last stage of a collision.
FIG. 14 is a cross-sectional view showing the structure of
Applicant's previous invention prior art.
DESCRIPTION OF THE PREFERRED EMBODIMENT
FIGS. 1 to 7 show an embodiment of the present invention. The
energy absorbing type intermediate shaft of the present invention
is characterized in that the dimensions of various constituent
members are regulated so that when an axial strong compressive
force is applied during a collision, a shaft 26 may be bent by a
small force before one end portion (the right upper end portion as
viewed in FIG. 1) of the shaft 26 bears against a member provided
on an end portion (the right upper end portion as viewed in FIG. 1)
of a tube 25. In the other points, the construction and action of
the present embodiment are substantially similar to those of the
energy absorbing type intermediate shaft of the aforedescribed
second and third examples of the prior art or of the aforedescribed
previous invention and therefore, the related portions as those in
the second and third examples of the prior art or the previous
invention are given the same reference numerals and overlapping
descriptions will be omitted or simplified herein, and chiefly the
characteristic portions of the present invention will hereinafter
be described.
The energy absorbing type intermediate shaft of the present
invention, like the energy absorbing type intermediate shaft of the
aforedescribed second and third examples of the prior art or of the
aforedescribed previous invention, is provided with the tube 25,
the shaft 26 and a displacement limiting portion 33. A pin 34 is
loosely inserted in circular holes 38 and 37 formed in a yoke 36
and a shock absorbing tube 35, respectively, constituting a first
universal joint 7 on the other end portion of the tube 25. This pin
34 corresponds to a member provided on an end portion of the tube
and to which one end surface of the shaft is opposed, and in the
structure of the aforedescribed second and third examples of the
prior art or of the previous invention, it forms the stopper
portion. Also, that portion of the intermediate portion of the
shaft 26 which is disposed apart from, in the axial direction, the
tube 25 is provided with a small cross-sectional area portion 39a
concentric with the shaft 26 and having a sufficiently small
diameter as compared with the other portions of the shaft 26. A
cover tube 27a which is a reinforcing member covers the
circumference of the portion in which this small cross-sectional
area portion 39a is formed. This cover tube 27a is supported around
the shaft 26 for displacement only in the axial direction (the
obliquely left to right direction as viewed in FIG. 1) thereof.
The small cross-sectional area portion 39a, as in the structure of
the aforedescribed previous invention, is formed into a pillar-like
shape concentric with the shaft 26, and the opposite ends of this
small cross-sectional area portion 39a and the body portion of the
shaft 26 are connected together by arcuate portions 43, 43. In the
present embodiment, concave grooves 44, 44 are formed at two
locations on the intermediate portion of the shaft 26 which
sandwich the small cross-sectional area portion 39a therebetween.
Through-holes 41, 41 are formed at two locations before and behind
the cover tube 27a which are aligned with these concave grooves 44,
44. The through-holes 41, 41 and the concave grooves 44, 44 are
filled with synthetic resin 42, 42, which are solidified.
A pressing portion 45 is formed on the outer peripheral surface of
the fore end side (the left lower end side) of the shaft 26. This
pressing portion 45 is formed by the rear end surface of a
large-diametered portion formed on that portion of the fore end
portion of the shaft 26 which is disposed apart from the cover tube
27a. When a strong compressive force resulting from a collision is
applied to the shaft 26, this pressing portion 45 is adapted to
bear against the other end edge (the fore end edge) of the cover
tube 27a and press this other end edge. The location at which this
pressing portion 45 is provided is regulated by the relation
between the location at which the small cross-sectional area
portion 39a is provided and the length of the cover tube 27a. That
is, design is made such that with the pressing portion 45 bearing
against the other end edge of the cover tube 27a, the end surface
of this cover tube 27a lies around the small cross-sectional area
portion 39a.
Accordingly, when the compressive force is applied, a change in
state occurs from a state as shown in FIG. 2 wherein the upper half
of one end edge of the cover tube 27a strikes against the upper
half of one end edge of the tube 25 via a state shown in FIG. 3 to
a state as shown in FIG. 5 wherein one end edge of the cover tube
27a and one end edge of the tube 25 bear against each other over
their entire circumferences. As the shaft 26 further moves toward
the other end side of the tube 25, the pressing portion 45 bears
against the other end edge of the cover tube 27a, whereupon the
small cross-sectional area portion 39a becomes present inside one
end edge of the tube 25.
Further, in the energy absorbing type intermediate shaft of the
present invention, that portion of one end edge of the cover tube
27a which is opposed to one end edge (the left lower end edge as
viewed in FIG. 1) of the tube 25 is inclined by an angle .theta. in
a direction in which one half side thereof separates more from one
end edge of the tube 25 than the other half side thereof. In the
present embodiment, the value of this angle .theta. is 10 degrees
(.theta.=10.degree.). Instead of or with end edge of the cover tube
27a, one end edge of the tube 25 may be inclined.
The sum of the distance .alpha. from the pressing portion 45 to the
other end edge (the left lower side end edge as viewed in FIG. 1)
of the cover tube 27a and the gap distance .beta. between one end
edge of the tube 25 and closest one end edge of the cover tube 27a
which are opposed to each other is made smaller than the distance
.gamma. from one end surface of the shaft 26 to the pin 34
supported on the other end portion of the tube 25
(.alpha.+.beta.<.gamma.). For example, .alpha.=28 mm, .beta.=2.5
mm and .gamma.=33.7 mm can be adopted as the values of these
distances .alpha., .beta. and .gamma., respectively. However, the
values of the distances .alpha., .beta. and .gamma. will suffice if
they satisfy .alpha.+.beta.<.gamma., and are determined with the
dimensions or the like of the tube 25 and other members taken into
account. Further, in the state shown in FIG. 3, one end surface of
the shaft 26 is spaced apart by a distance a from the pin 34 as
shown in FIG. 4 (0<a<.gamma.), and in the state shown in FIG.
5 wherein one end edge of the cover tube 27a and one end edge of
the tube 25 bear against each other over their entire
circumferences and the amount of entry of the shaft 26 into the
tube 25 has increased from the state shown in FIGS. 3 and 4, the
dimension of each constituent member is regulated so that said one
end surface may be spaced apart by a distance b (0<b<a) from
the pin 34 as shown in FIG. 6.
The energy absorbing type intermediate shaft of the present
invention constructed as described above is incorporated into the
steering apparatus of an automobile and transmits the movement of
the steering wheel 2 (FIG. 8) to the steering gear. During normal
operation, the cover tube 27a is present around the small
cross-sectional area portion 39a on the basis of the restraining
force of the synthetic resin 42, 42. Therefore, shaft 26 does not
bend at the small cross-sectional area portion 39a. A torque for
steering is transmitted from the rear portion (the right portion as
viewed in FIG. 1) to the fore portion (the left portion as viewed
in FIG. 1) of the shaft 26 chiefly by the cover tube 27a.
When an axial strong compressive force is applied during a
collision, the restraining force of the synthetic resin 42, 42 is
lost. As in the case of the structure of the aforedescribed
previous invention, the shaft 26 and the tube 25 are then axially
displaced a change in state occurs from the state shown in FIG. 1
to a state as shown in FIG. 2 wherein the upper half of one end
edge of the tube 25 and the upper half of one end edge of the cover
tube 27a bear against each other. From this state, the shaft 26 is
further moved rearwardly, whereby from the state shown in FIG. 2,
the abutting surfaces of the tube 25 and the cover tube 27a are
axially moved relative to the shaft 26 as shown in FIG. 3, and
these abutting surfaces become present around the intermediate
portion of the small cross-sectional area portion 39a. In the state
shown in FIG. 3, one end surface of the shaft 26 is spaced apart by
a distance a from the pin 34 as shown in FIG. 4. Also, in this
state shown in FIG. 3, the pressing portion 45 bears against the
other end edge of the cover tube 27a.
When from such a state shown in FIG. 3, the above-mentioned
compressive force is further applied, the cover tube 27a is pushed
and the previously coaxial axes of this cover tube 27a and the tube
25 bend as shown in FIG. 5, and one end edge of the former and one
end edge of the latter bear against each other over their entire
circumferences. At this time, the shaft 26 tends to be pushed
farthest into the tube 25, and the distance between one end surface
of the shaft 26 and the pin 34 changes from distance a shown in
FIG. 4 to distance b shown in FIG. 6. As described above, in the
present invention, when the shock of a collision or the like is
applied, the dimension of each constituent member is regulated so
that even when one end surface of the shaft 26 approaches the pin
34 at its maximum, these may not bear against each other. After the
state shown in FIGS. 5 and 6, the shaft 26 plastically deforms the
small cross-sectional area portion 39a and thereby bends as shown
in FIG. 7. By the small cross-sectional area portion 39a being thus
plastically deformed, energy based on the collision is absorbed to
thereby alleviate the shock applied to a driver's body. The action
when the shock is thus alleviated is generally similar to that in
the case of the structure of the previous invention.
However, in the case of the energy absorbing type intermediate
shaft of the present invention, the dimensions .alpha., .beta. and
.gamma. are regulated so as to be .alpha.+.beta.<.gamma. and
therefore, when a strong compressive force is applied with a
collision, the shaft 26 bends without one end surface thereof
bearing against the pin 34. Accordingly, the shaft 26 is bent by a
small force. That is, in the present invention, the dimension of
each constituent member is regulated so that even when as shown in
FIG. 6, one end surface of the shaft 26 approaches the pin 34 at
its maximum, said one end surface and the pin 34 may not bear
against each other. Accordingly, when the cover tube 27a, the tube
25 and the shaft 26 change from the state shown in FIGS. 3 and 4 to
the state shown in FIGS. 5 and 6, the retraction of the shaft 26,
i.e., an increase in the amount of entry of the shaft 26 into the
tube 25, takes place smoothly. As a result, the force required for
the bending of the small cross-sectional area portion 39a may be
small. Also, since one end of the shaft 26 does not bear against
the pin 34, a strong pressure force is not applied to this pin 34.
Therefore, it is not necessary to make the rigidity of the pin 34
as great as that of the pin 34 of prior art FIGS. 10, 11 and 14.
Thus, the manufacture of the pin 34 can be simplified. As a result,
the ease of the manufacture and a reduction in the cost of
manufacture of the entire energy absorbing type intermediate shaft
can be achieved.
When the present invention is to be carried out, the dimensions of
the small cross-sectional area portion 39a can also be regulated as
in the previous invention to thereby prevent an increase in cost
resulting from highly accurate working and achieve a reduction in
the cost of manufacture of the energy absorbing type intermediate
shaft. Further, in the illustrated embodiment, spline engagement is
adopted as the rotation preventing structure for the tubes 25, 27a
and shaft 26, but instead thereof, other known rotation preventing
structure such as engagement between flat surfaces opposed to each
other can also be adopted. Also, the structure for preventing the
cover tube 27a from being displaced in the axial direction of the
shaft 26 during normal operations need not always resort to the
synthetic resin 42, but other structure can also be adopted such as
pressing-in the fitting of an elastic ring or the like, or
structure in which steel balls are pressed into a concave groove
formed in one of the inner peripheral surface of the cover tube 27a
and the outer peripheral surface of the shaft 26.
The energy absorbing type intermediate shaft of the present
invention is constructed and acts as described above and therefore,
can secure sufficient energy absorbing capability and yet can
reduce the number of parts and simplify the assembling work to
thereby achieve a reduction in the cost of manufacture. Further,
the bending of the shaft can be accomplished by a small force and
also, the rigidity of a member such as the pin provided on the
other end portion of the tube need not be made particularly great
with a compressive force applied during a collision being taken
into account. Therefore, the securement of energy absorbing
capability during a collision becomes more sufficient and the
inexpensiveness and lighter weight of the member can be achieved.
Thus, from this, a reduced cost of manufacture and lighter weight
of the entire energy absorbing type intermediate shaft can be
achieved.
* * * * *